Editing an equation?

[DafyddJohn]

Hi

I've only just purchased my copy of DPlot so I hope you'll forgive this, hopefully, easy question.

I can see how to display a graph via Generate->Y=f(x), but I can't see a way to simply edit it. As far as I can see you have to delete the curve and then put the new one in e.g.

If I start with Y = x^2 I can't change it to 2*x^2 + 3*x - 2 without adding this new curve i.e. I can't edit the first one.

I've obviously missed something obvious. Can anybody help?

Thanks in advance

Dave

[DPlotAdmin]

I've obviously missed something obvious. Can anybody help?

You haven't missed anything; that's the way it works (mostly, see below). The reason for that is fairly simple: DPlot only cares about the data produced by the equation, not the equation. It is a data plotter rather than a grapher. It would not be possible to do what you want w/o severely limiting what can be done with curves produced by equations. Almost all of the commands on the Edit menu would have to be disabled for equations or nothing would make sense. For example, if I manually change the Y values of a couple of data points, then change the equation, what should happen?

You can, though, perform an operation on the original curve that does what you want in your example. If you start with Y=X^2, you can use Edit>Operate on Y with Y=Y+X^2+3*X-2.

The "mostly, see below" comment: Some users who have asked a similar question have it stuck in their head that there can be only one equation per document, and that's where "you have to delete the curve" comes from. I don't know if this is the case with you, but just so we're clear: there's no need to delete the original curve unless that's really what you want to do.